See here: [https://berryberry.hatenablog.jp/](https://berryberry.hatenablog.jp/entry/2022/03/14/032052)

First of all, this challenge is to send a correct input to the server.

## Given File
I obtained an executable file named "file" and opened it in ghidra.
I changed some function name for understand.

First, this program receives input in line 11.
In line 17, the input function checks input format.
The input format is like "num;num;num;...;num".

Between line 18 and line 21, the check1 function determines whether the quotient and remainder of the iva1 variable divided by 14 are between 0 and 13 or not. If it's not, then it displays "cheater". Therefore, we can choose numbers between 0 and 195.
In line 22, the check2 function determines whether all 196(=14*14) characters beginning with &DAT_00104100 are 0x2d(-) or 0x2a(*).

Now, what is a string begins with &DAT_00104100 ?
Look at line 16, the initialization function calculates the remainder of the pseudorandom number divided by 14 and replaces the &DAT_00104100 index with 2a. It also process other things.
## Solution
The solution is to find the input number which does not display "BOOM" in the check1 function.
I spent much time to find a solution using the rand function in the initialization function. However, i coudn't, so I looked for a number which does not display "BOOM" in the check1 function one by one.

Here is the correct input.

Finally, my writeup may help you understand this program, but may not be good for people who want to solve it correctly. Thank you.